After hatching from eggs, lobsters spend a certain period of time as larvae. For example, spiny lobsters spend approximately one year as phyllosoma larvae, then metamorphose into puerulus/nisto larvae, and then metamorphose into juvenile lobsters. Since lobsters are relatively expensive, high in demand, and important aquatic resources, there is a high need for a technology for producing a large amount of lobster seeds and seedlings in a stable manner. It is difficult, however, to artificially feed and rear phyllosoma larvae. At present, they are only grown in unit of several individuals in small tanks in the field of fisheries experimental research.
Reasons why phyllosoma larvae are difficult to artificially rear include: (a) appropriate baits are limited; (b) the larvae are likely to sink to the bottom of the tank and prone to microbial contamination by feces and uneaten baits present on the bottom of the tank; and (c) their peculiar shape is easily broken by interference between individuals. In a known method of artificially rearing spiny lobster larvae, the first-stage phyllosoma larvae of spiny lobsters are fed with Artemia nauplii and in the second and following stages are fed with Artemia nauplii and pieces of mussel meat, in particular gonads of blue mussel (see Japanese Patent No. JP 2525609, and Hirokazu Matsuda, “Studies on the larval culture and development of Panulirus lobsters”, Nippon Suisan Gakkaishi, The Japanese Society of Fisheries Science, 2006, vol. 72 (5), pp. 827-830). It is not practical, however, to adopt this method to artificially rear a large number of larvae, because it is difficult to collect a large number of fresh blue mussel gonads on a regular basis.
In other known methods, crustacean larvae are reared in slowly rotating tanks to prevent the larvae from sinking (see Japanese Unexamined Patent Publication No. JP 2002-262702 and Japanese Patent No. JP 3955947). These methods have a disadvantage of high rearing cost, because they rely on complicated and expensive apparatus. Furthermore, no technology has been developed so far to keep individual larvae apart from each other with more than a certain distance between them.